This supplement is for partial support of our Protein Sequence and Structure Reference Data Center and Information Resource. This center maintains a complete, currently correct, continuing collection of protein data and files of background information including evolutionary history, distant relationships, alignments, genetic relationships and results from X-ray crystallography on the three-dimensional structure of proteins. Data entries are prepared in a uniform format. One sequence for each protein structure is selected for presentation while comments and references to the work of other laboratories are included. A computer tape of the sequence data will be prepared for distribution. Manuscripts for two supplementary volumes to the Atlas of Protein Sequence and Structure Vol. 5, including sequence data, explanatory material, indexes and summaries of the data, are to be prepared. Segment dictionaries will be prepared for distribution. Data searches and other computer services involving the up-to-date sequence data collection will be performed at cost for other researchers upon request.